This invention relates to spot-type disc brakes and more particularly to a guiding device for brake pad supports of a spot-type disc brake with at least one pad positioning pin seated in a bore of the brake housing and frictionally engaged with a brake pad support.
In guiding devices of this type, the inactivated position of the brake pad support is determined by its position relative to the pin, which position is adjusted by its frictional connection with the pad positioning pin. The possible return stroke of the pin produces the brake clearance. The return movement of the brake piston is generally brought about by the initial tension of the ring seal on the actuation piston, as soon as the actuation of the piston causing abutting engagement of brake pad with brake disc stops. In order to ensure the return movement of the brake pad away from its engagement with the brake disc at all times, the introduction of return springs has become customary. These springs either act directly on the brake pad or, alternatively, on one or more positioning pins. In the latter case, it has been made sure that, on the one hand, the resilience of the spring is high enough to ensure that the brake pad disengages from the brake disc safely and, on the other hand, not so high as to overcome the frictional connection between the pad positioning pin and the pad support. This is to say that the springs used must be carefully selected as to their characteristics, i.e. they must be manufactured with little dispersion. Return springs acting axially on the pad positioning pin should have a steep characteristic in order to permit a displacement of the pad support by overcoming the frictional connection when the brake pad is worn out. To meet all of these requirements, the return spring must be one with a selected characteristic and extremely close tolerance.